WAEC Chemistry 2015 Paper

Concept:An acid salt is formed by partial neutralisation of a polybasic acid, so it still contains one or more replaceable hydrogen atoms.Explanation:$\mathrm{NaHSO}_4$ is sodium hydrogensulphate.It is obtained by the partial neutralisation of sulphuric acid, $\mathrm{H}_2\mathrm{SO}_4$, with sodium hydroxide.Only one hydrogen atom of the acid is replaced by sodium, leaving one acidic hydrogen in the salt.So $\mathrm{NaHSO}_4$ has replaceable hydrogen and therefore behaves as an acid salt.$\mathrm{CH}_3\mathrm{COONa}$ is a normal salt.$\mathrm{Mg(OH)Cl}$ is a basic salt because it contains unneutralised hydroxyl ions.$(\mathrm{NH}_4)_2\mathrm{SO}_4$ is a normal salt, even though its solution is acidic due to hydrolysis.Hence, the acid salt among the options is $\mathrm{NaHSO}_4$.Answer:C. $\mathrm{NaHSO}_4$